A liquid crystal display device is used in various fields of OA equipments such as a personal computer and a television set, taking advantage of the features such as light weight, thin shape, and low power consumption. In recent years, the liquid crystal display device is used also as displays for a portable remote terminal such as a cellular phone and PDA (personal digital assistant), a car navigation equipment, and a game machine.
By the way, in a liquid crystal display device, voltage is applied to upper and lower sides of a liquid crystal layer, for example, to change transmissivity by changing alignment state of liquid crystal molecules. Thereby, images are displayed. However, when the direct-current driving in which polarity of the applied voltage is not changed is adopted, since electric distribution changes by existence of ion impurities in the liquid crystal layer, etc., display grace of the images falls. Therefore, it is common to adopt an alternating current driving system which inverts polarity of the applied voltage every predetermined interval.
As the AC driving system, a frame inversion driving system, a column (image signal line) inversion driving system, a line (scanning signal line) inversion driving system, a dot inversion driving system, etc., are known. Among the driving systems, since the dot inversion driving system is a system which inverts the polarity of the voltage applied to every adjacent pixel, neither flicker nor cross talk is visible easily. Therefore, the dot inversion driving system has feature that uniform luminance distribution is acquired. However, comparing with other driving systems, there is demerit in which power consumption is large. Therefore, a pseudo-dot inversion driving system is proposed. The pseudo-dot inversion driving system has both features of the column inversion driving system effective in low power consumption, and the dot inversion driving system effective in display grace. That is, the same polarity image signals are applied to the column lines for one frame period, and different polarity images are applied to adjacent pixels, i.e., the dot inversion display is performed as a polarity pattern on the display panel.
When the column inversion driving system is adopted, fall of the display grace, such as vertical cross talk may occur. The vertical cross talk is a phenomenon in which luminance changes in a stripe in regions on upper and lower sides of a window when the window is displayed in a background display.
Since the vertical cross talk remarkably reduces the display grace, it is necessary to prevent the fall of the display grace due to the generation of the vertical cross-talk.